1. Field of the Invention
The present invention relates to a method and apparatus for use in the oil industry, and, more particularly, to a method and apparatus for providing surge reduction functionality while running a casing liner downhole.
2. Description of the Prior Art
The principle of operation of a surge reduction tool is described in U.S. Pat. No. 5,960,881 (xe2x80x9cthe ""881 patentxe2x80x9d), which is incorporated herein by reference and which should be referred to with respect to the advantages provided by that invention. In practice, the invention of the ""881 patent has provided the oilwell industry with the long-desired capability of running in casing liners faster and more reliably with a minimum of lost drilling mud.
While the device of the ""881 patent provided for the first time a mechanism for reducing surge pressure, circumstances may be encountered during the running downhole of a casing liner where even a tool in accordance with the ""881 patent may be rendered ineffective to reduce surge pressure. Specifically, if a casing liner encounters a tight hole condition or bridge while being lowered into the wellbore, it is not possible to effectively circulate mud around the end of the casing liner to help free it. This is because the surge pressure reduction flow ports of the apparatus in accordance with the ""881 patent are open to the annulus and will short-circuit flow to the annulus above the casing liner. If this happens, the driller may establish circulation by dropping the drop ball before reaching the target depth to close the open ports of the surge reduction tool. The driller may then use the mud pumps to clean up and wash out the borehole. Once the driller makes this decision, however, he must attempt to lower the casing liner to the target depth without further benefits of surge reduction, since the tool can only be functioned once.
Accordingly, the oil industry would find desirable a surge reduction tool that allows an additional sequence of opening and closing of the flow ports to provide alternation between the xe2x80x9csurge reductionxe2x80x9d and the xe2x80x9ccirculationxe2x80x9d modes of operation. In other words, a tool would be desirable which provides surge reduction, which allows for circulation to be established in the event the casing encounters tight hole conditions, and which provides surge reduction after the borehole conditions are improved.
The oil industry has seen other devices that claim to regulate communication between the wellbore annulus and the well fluid; however, none of these devices provides surge reduction functionality. U.S. Pat. No. 3,457,994, assigned on its face to Schlumberger Technology Corp., discloses a well packer apparatus with a pressure-powered valve and locking latch device which can be initially set between open and closed conditions and lowered into a wellbore on a running-in string. However, the pressure-powered valve is opened and closed by an actuator, not indexed by a drop ball. In addition, the stated purpose of the ""944 device is to regulate the passage and removal of the commodity within the well, not to facilitate surge reduction of a downhole tool.
U.S. Pat. No. 3,517,743, assigned on its face to Dresser Industries, Inc., provides a selective interval packer device which permits fluid to pass through a seated ball valve during descent into a wellbore and which aligns with a selectively indexed location along the wellbore. However, the stated purpose of the device is to isolate and communicate with formations at selected intervals. The opening of the ball valve to permit fluid flow through the packer device and the indexed regions along the wellbore facilitate this purpose and do not provide a means to reduce surge pressure during the running of casings.
U.S. Pat. No. 5,730,222 (xe2x80x9cthe ""222 patentxe2x80x9d), assigned on its face to Dowell, provides a downhole circulating sub device to direct or divert fluid flow between a measurement while drilling (MWD) tool and a flow activated motor and drill bit. The sub device is connected between the upper MWD tool and the lower drill bit, and may be activated and deactivated by a respectively pushing or pulling on a coiled tube. When activated, the sub device directs flow to the flow activated motor and drill bit. Once deactivated, the sub device short-circuits the drill, but still allows for flow through the MWD tool (the ""222 patent, FIGS. 1 and 2). However, device of the ""222 patent is manipulated by physically pushing or pulling on a coil tube and not by a dropping a ball through drill string and into apparatus to open or close the flow ports. Furthermore, the stated purpose of the device of the ""222 patent is to direct fluid flow into or divert fluid flow from a downhole flow activated tool, and not to implement surge pressure reduction.
Subsequent to the invention of the ""881 patent, others have attempted to produce apparatus which provides surge reduction. Baker Hughes began to offer apparatus which functions in accordance with the ""881 patent. Also, in U.S. Pat. No. 6,082,459 (xe2x80x9cthe ""459 patentxe2x80x9d), assigned on its face to Halliburton, a diverter apparatus is disclosed for reducing surge pressure while running a casing liner in a partially cased well bore. Halliburton is believed to market this device as the xe2x80x9cSuperFillxe2x80x9d system. According to the ""459 patent and Halliburton""s literature, the SuperFill system is movable from a closed port position to an open port position and vice versa.
The diverter device shown in FIG. 3B of the ""459 patent comprises an inner tubular housing, an outer sliding sleeve, and a system of drag springs arranged outside and surrounding the sliding sleeve. In operation, the diverter is run downhole where the springs directly engage a previously cemented casing liner. As the springs engage the casing liner, the drag springs compress and drag the outer sliding sleeve relatively upwards with respect to the inner housing into an open port position. To move the apparatus from the open to the closed position, the ""459 patent states that downward movement is stopped and an upward pull is applied so that the tubular housing moves upwardly until the sliding sleeve covers the flow ports in the inner tubular housing. According to the ""459 patent, the diverter apparatus includes a J-slot so that the diverter can be locked in the closed position by rotating the drill string.
In practice, it is believed that substantial problems may be encountered in use of the tool of the ""459 patent. For example, one would not want to move the tool of the ""459 patent from an open port position to a closed port position without also locking the tool in the closed port position. This is because the weight of the casing liner may cause the tool to trip to the open port position, if not locked. To lock the tool of the ""459 patent, it is rotated to the right. This rotation also causes the running tool and casing liner to rotate. If the rotating casing liner gets caught in the borehole, the continued rotation can result in the running tool becoming disengaged from the casing liner. To avoid this disastrous result, the casing liner in practice is set on the bottom of the borehole before the diverter apparatus is locked in the closed position. This result is undesirable, since the casing liner cannot be properly cemented in place under these conditions.
A tool as described in the ""881 patent includes a finger latching apparatus to latch the sliding valving sleeve apparatus into position. When the casing liner has reached target depth, a ball is pumped down the drill string until it lands in a yieldable seat that is contained within the latched valving sleeve. Once the ball has landed in the yieldable seat, pressure is increased until the pressure end load force overcomes the latched spring fingers and allows the valving sleeve to move into a lower position that closes the vent ports. The pressure is then increased further until the seat yields to an extent that allows the ball to pass through the seat and on down to the bottom of the borehole. In the embodiment of the invention of the ""881, the release pressure can vary from tool to tool, because the release pressure is primarily controlled by the flexibility of the spring fingers and the friction between the spring fingers and the inner surface of the sleeve.
In accordance with the present invention, apparatus for reducing surge pressure while running a tubular in drilling fluid in a borehole is provided.
The apparatus of the present invention comprises a housing having a top and having a bottom end for connection to a casing hanger. The housing has at least one set of housing flow ports formed therein. The housing is suspended from the drill pipe, and the drill pipe provides a communication conduit between the drilling rig and the wellbore.
Apparatus in accordance with the present invention further comprises a sleeve within the housing, and the sleeve has at last two sets of sleeve flow ports which are located at different axial locations on the sleeve. Initially, the sleeve is positioned in the housing such that a first open port condition exists. Indexing apparatus is provided for axially moving the sleeve from the first open port position to a first closed port position, from the first closed port position to a second open port position, and from the second open port position to a second closed port position.
The indexing apparatus preferably includes a camming sleeve and spring washers which provide a tool in accordance with the present invention with a more predictable release pressure than has heretofore been available.
Another feature of the surge reduction tool of the present invention is a dart directing sleeve in the housing which has a smaller, smoother bore than the drill string and provides the important function of aligning the dart before it lands in the seat so that the dart resistance when passing through the seat is minimized.
Yet another feature of the improved tool of the present invention are chevron seals arranged in the housing above and below the vent port which reduces the potential for hydraulic lock and provides a seal mechanism that is more reliable while running in downhole conditions.